1. Field of the Invention
The present invention relates to a probe used for testing the operation of semiconductor integrated circuits which are formed on semiconductor wafers, a method of the same, and a member for removing metals, metal oxides, contaminants obstructing electrical contact, etc. which are adhering to the probe.
2. Description of the Related Art
In a conventional probe, as shown in FIG. 22A, a testing (probing) is carried out by attaching a probe 202 having a fore end bent into a hook-like shape to a probe card 201 which is vertically movable, and pushing the probe 202 against a test pad of a semiconductor integrated circuit (referred to as a pad hereinafter) in such a condition that an oxide film on the pad surface is broken off to establish true contact (electrical contact) between the probe and a fresh surface of the pad. The condition of a probe tip under the probing is shown in FIG. 22B. For the sake of explanation, FIG. 22B is illustrated in the form of a simplified model with respect to dimensions and so on. A tip 200 of the conventional probe 202 is originally finished to have a flat end face, as shown in FIG. 22B. Even when the probe tip is machined to have a spherically curved surface intentionally, a sphere approximating the curved surface has a radius R of curvature as large as 20-30 xcexcm. At the time of probing, therefore, the whole of flat end portion first comes into contact with a pad 203 while an oxide film 204 and contaminants on the surface of the pad 203 are interposed between the probe tip and the pad surface. Then, as the probe 202 is more closely pushed against the pad 203, the oxide film 204 on the surface of the pad 203 is partly broken off to produce an electrical continuity region 206 in which electrical true contact can be established, thereby enabling a continuity test to be performed. With repetition of the probing, however, the oxide film 204 is accumulated on a heel portion 205 of the probe 202 which is subject to maximum stresses, and an area of the true contact with the pad 203 is so reduced as to make electrical continuity unstable. To reliably establish the electrical contact, vibration is applied to the probe tip in Japanese Unexamined Patent Publication No. 6-18560, for example.
Further, tungsten used as materials of the probe 202 is in the form of a powder sintered compact which has material defects (voids) therein. Accordingly, when the powder sintered compact is machined so as to provide a tip shape of the probe 202, the material defects appear on the probe surface. Pad materials such as aluminum, for example, enter the material defects appearing in the tip (end) face of the probe 202 to form deposition nuclei and grow into deposits. As a result, contact resistance is increased.
For removing those material defects, heat treatment is applied to tungsten materials in Japanese Unexamined Patent Publication No. 5-140613, for example.
In addition, the card probe 202, which serves as an interface for electrical signals transferred between a tester for measuring electrical characteristics of a semiconductor integrated circuit formed on a wafer, and the semiconductor integrated circuit, is brought into pressure contact with the pad 203 of the semiconductor integrated circuit in such a manner as to scrape off an aluminum alloy forming the pad 203. Therefore, scraped-off parts of materials of the pad 203, such as aluminum and an aluminum oxide, and/or of contaminants remaining on the surface of the pad 203 adhere to the tip of the probe 202. Unless those adhering substances or deposits are removed from the tip of the probe 202, the contact resistance between the probe 202 and the pad 203 is so increased that the electrical characteristics of the semiconductor integrated circuit cannot be accurately measured. In other words, if the probe 202 is used for a long period of time with the deposits kept accumulated on the tip of the probe 202, the contact resistance increases over time.
For those reasons, it is customary to clean out the tip of the probe 202 and remove foreign matter adhering to it whenever the probing is repeated a predetermined number of times.
For example, Japanese Unexamined Patent Publication No. 7-244074 discloses an abrasive sheet formed by mixing fine-grained abrasives for grinding in an elastic matrix and then shaping the matrix into a sheet. The abrasive sheet is attached, instead of a semiconductor wafer, onto a wafer moving table of a probe apparatus which is operated to made a semiconductor integrated circuit and a probe contacted with each other. The wafer moving table is vertically moved to press a tip of the probe against the surface of the abrasive sheet, whereupon contact friction is caused between the tip face of the probe and the fine-grained abrasives dispersed in the abrasive sheet to remove foreign matter adhering to the probe tip.
Thus, in the conventional probe having the above-described construction, as shown in FIG. 22B, the true contact area (electrical continuity region 206) between the tip 200 of the probe 202 and the pad 203 is very small during the test of electrical characteristics. Accordingly, a sufficient degree of electrical continuity is not obtained between the probe 202 and the pad 203 in some cases.
Also, voids produced in tungsten materials of the probe 202 are conceivably eliminated by heat treatment. However, if the tungsten materials are subject to heat treatment at a temperature not lower than the recrystallization temperature, there arises another problem that the probe materials become brittle.
Further, the conventional abrasive sheet for removing foreign matter adhering to the tip 200 of the probe 202 is formed by mixing fine-grained abrasives in an elastic matrix and is deformed upon the tip 200 of the probe 202 being pressed against the surface of the abrasive sheet. As shown in FIG. 23, therefore, the tip 200 of the probe 202 is forced to come into a matrix 210 and abraded by fine-grained abrasives 211 over a region indicated by dotted lines. This tip abrasion raises a problem that, with repetition of cleaning, the probe tip is thinned and eventually loses strength to such an extent that it may bend or chip.
With a view of solving the problems mentioned above, an object of the present invention is to provide a probe which can increase a true contact area between a probe tip and a pad and hence establish reliable electrical contact.
Another object of the present invention is to provide a member for removing foreign matter adhering to the probe tip, which can prevent the probe tip from being thinned with repetition of cleaning and hence has a longer service life.
To this end, according to the present invention, there is provided a test probe for semiconductor devices, the test probe having a tip portion which is pressed against a test pad of a semiconductor device to establish electrical contact between the tip portion and the pad for testing the operation of the semiconductor device, wherein the probe is formed to have a tip shape with an angle of not less than 15 degrees formed at the surface of the pad between a tangential line with respect to a tip face of the probe and the pad surface when the probe is pressed against the pad, the tip shape of said probe having a spherical surface meeting the relationship of:
xcex8=cosxe2x88x921(1xe2x88x92t/R)xe2x89xa715xc2x0
where the radius of curvature of the spherical surface is R, the thickness of the pad is t, and the angle formed at the pad surface between the tangential line with respect to the probe tip face and the pad surface when the probe is pressed against said pad is xcex8, the probe having a flat portion at an end of the tip portion.
According to another aspect of the present invention, there is provided a method of manufacturing a test probe for semiconductor devices, the test probe having a tip portion which is pressed against a test pad of a semiconductor device to establish electrical contact between the tip portion and the pad for testing the operation of the semiconductor device, wherein the probe is made of a linear metal material prepared by sintering powdered raw materials, and is subject to heat treatment in an atmosphere of non-oxidizing gas under such conditions that a treatment temperature is not higher than the recrystallization of the metal material and the pressure of the non-oxidizing gas is raised to a level at which the volume of the metal material contracts over time.
According to another aspect of the present invention, there is a member for removing foreign matter adhering to a probe tip, wherein the member comprises a resin member capable of elastic deformation, a first metallic member formed on the surface of said resin member as a film having predetermined tensile strength, and a ceramic member formed on the surface of the metallic member as a film having a predetermined thickness.
According to another aspect of the present invention, there is a member for removing foreign matter adhering to a probe tip, wherein the member comprises a resin member having a Young""s modulus of 100-400 kgf/mm2, a metallic member formed on the surface of the resin member as a film having a tensile strength of not less than 20 kgf/mm2 and a thickness of 50-150 angstroms, a nickel plated layer formed on the surface of the metallic member in a thickness of not more than 5 microns, and ceramic particles fixedly dispersed in the nickel plated layer and having a diameter smaller than the thickness of the nickel plated layer.
According to another aspect of the present invention, there is a member for removing foreign matter adhering to a probe tip, wherein the member comprises a resin member having a Young""s modulus of 100-400 kgf/mm2, a metallic member formed on the surface of the resin member as a film having tensile strength of not less than 20 kgf/mm2 and a thickness of 50-150 angstroms, a nickel plated layer formed on the surface of the metallic member in thickness of not more than 5 microns, and silicon particles or silicon carbide particles fixedly dispersed in the nickel plated layer and having a diameter smaller than the thickness of the nickel plated layer.